Abstract: We present a measurement of the W-boson helicity fractions in single-top events topology in muon+jets final state using LHC pp collisions at 7 TeV and 8 TeV center-of-mass energies. The datasets are collected by the CMS detector during 2011(A) and 2012 (A+B) runs, respectively corresponding to an integrated luminosity of 1.14 fb-1 and 5.3 fb-1.
The combination of the two measurements yields
FL=0.293 +- 0.069 (stat.) +- 0.030 (syst.)
F0=0.713 +- 0.114 (stat.) +- 0.023 (syst.)
FR=0.006 +- 0.057 (stat.) +- 0.027(syst.).
The measured polarizations are used to set limits on tWb anomalous couplings. Similar technique is used to measure the W-helicities in the electron and muon channels using the entire data of 2012.